Inherited forms of hyperlipidemia can account for at least 30% of myocardial infarctions in male under the age of 50. Familial hypercholesterolemia and familial combined hyperlipidemia are known risks for coronary artery disease, recently familial hypertriglyceridemia has been suggested not to be associated with increased coronary artery disease. This proposal was aimed at looking at patients with hypertriglyceridemia in familial hypertriglyceridemia and familial combined hyperlipidemia by evaluation of very low density lipoprotein production and removal rates in vivo, and in vitro in skin fibroblasts, to understand mechanisms of pathophysiology of the two disorders. This information will be used as a marker for simple identification and further to direct therapy towards a specific site of the metabolic abnormality. BIBLIOGRAPHIC REFERENCES: Brunzell, J.D., Robertson, R.P., Lerner, R.L., Hazzard, W.R., Ensinck, J.W., Bierman, E.L. and Porte, D., Jr.: Relationships between fasting plasma glucose levels and insulin secretion during intravenous glucose tolerance tests. J. Clin. Endocrinol. and Metab. 42:222-229, 1976. Brunzell, J.D., Schrott, H.G., Motulsky, A.G. and Bierman, E.L.: Myocardial infarction in the familial forms of hypertriglyceridemia. Metabolism 25:313-320 , 1976.